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CST - BIOSCI107 > ET : N - Synaptic Transmission > Flashcards

ET : N - Synaptic Transmission Flashcards

1
Q

what is synaptic transmission

A

the process of transferring information between neurons or between neurons and muscle fibres

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2
Q

synaptic transmission occurs between neurons through either of which two things?

A

chemical synapses
or
electrical synapses (via gap junctions)

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3
Q

where is the neuromuscular junction

A

outside the brain in skeletal muscle

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4
Q

describe the process of using the neuromuscular junction as a model of (excitatory) synaptic transmission

A
  • action potential arrives to presynaptic terminal
  • action potential invades terminal and activates voltage-gated Ca2+ channels increasing influx of Ca2+
  • release of transmitter (acetylcholine) by exocytosis
  • reaction of transmitter with post synaptic receptors
  • activation of ligand-gated ion channels
  • post-synaptic EPP and action potential
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5
Q

what is the ionic mechanism of end-plate potentials (EPP)

A

transient opening of ion channels selective to both Na+ and K+ (non-selective cationic channels)

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6
Q

end-plate potential is always

A

suprathreshold

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7
Q

end-plate potential is always suprathreshold which means

A

always triggers an action potential

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8
Q

when EPP triggers AP, where does it go

A

transmitted along the muscle fiber

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9
Q

what are neurotransmitters

A

chemical messengers that open (or sometimes close) ion channels, and lead to depolarisation or hyperpolarisation of post-synaptic membrane

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10
Q

what are the two types of chemical synapses in CNS

A

excitatory synapses and inhibitory synapses

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11
Q

what do excitatory synapses evoke

A

depolarisation of the postsynaptic membrane called excitatory postsynaptic potential (EPSP)

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12
Q

what do inhibitory synapses evoke

A

hyperpolarisation of the postsynaptic membrane called the inhibitory postsynaptic potential (IPSP)

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13
Q

what is the ionic mechanism of EPSPs (and what does this do to the RMP?)

A

the transient opening of channels selective for Na+, K+ and sometimes Ca2+

this shifts Vm of RMP towards the threshold for generation of an AP

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14
Q

what is the ionic mechansim of IPSPs

A

often through the transient opening of K+ channels

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15
Q

what is the main neurotransmitter of EPSPs

A

glutamic acid or ACh

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16
Q

what is the main neurotransmitter of IPSPs

A

GABA or glycine

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17
Q

what causes IPSPs

A

increase of cell membrane permeability to K+ function by hyperpolarising the cell membrane

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18
Q

IPSPs work ________________ of EPSPs and thus IPSPs do not need to be evoked before or after the occurrence of EPSPs

A

independently

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19
Q

does synaptic transmission have a delay

A

yes a very minor one

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20
Q

how are neurotransmitters classified

A

based off of chemical structure

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21
Q

what are the two classifications of neurotransmitters

A

small molecule neurotransmitters (classical neurotransmitters)

neuropeptides (neuromodulators)

22
Q

what is larger, neuropeptides or small molecule neurotransmitters

A

neuropeptides

23
Q

small molecule neurotransmitters: speed of action and interaction with postsynaptic receptors

A

usually fast action and direct on postsynaptic receptors

24
Q

small molecule neurotransmitters: amino acids

A

glutamate, GABA, glycine, ACh

25
Q

small molecule neurotransmitters: amines

A

serotonin (5-HT), noradrenaline, dopamine

26
Q

effect of neuropeptides on postsynaptic receptors or other neurotransmitters

A

they are large molecule chemicals that have an indirect action on postsynaptic receptors or modulatory action on the effects of other neurotransmitters

27
Q

speed of action of neuropeptides

A

slow and usually more diffuse action

28
Q

what are four examples of neuropeptides that are involved in communication between neurons

A

neuropeptide Y (NPY), substance P, kisspeptin and enkephaln

29
Q

what are the three factors that determine synaptic action

A

1) the type of neurotransmitter/neuromodulator
2) the type of neurotransmitter receptor/channel complex expressed in the postsynaptic membrane
3) the amount of neurotransmitter receptor present in the postsynaptic membrane

30
Q

what are the three main subtypes of glutamate receptors in the post synaptic membrane

A

AMPA, NMDA and kainate

31
Q

the post synaptic effect depends on

A

which receptor the amino acid acts on

32
Q

what is the main difference between AMPA and NMDA

A

when AMPA receptor channel is activated it opens and is non-selectively permeable to sodium and potassium, so the cell membrane depolarises. but, in NMDA, when it is activated, it becomes permeable to not only sodium and potassium, but also to calcium

33
Q

what are AMPA, NMDA and kainate gated by

A

chemical glutamate

34
Q

which receptor is permeable to calcium

A

NMDA

35
Q

what happens with too much gultamate and too much activation of NMDA receptor

A

may cause excessive entry of calcium and damage the cell or completely destroy it

36
Q

when we have more synaptic receptors, post-synaptic event will be

A

larger and vice versa

37
Q

why is removal of neurotransmitters necessary

A

to allow a new signal to follow rapidly

38
Q

what are the three main mechanisms of removal of neurotransmitters

A

diffusion
enzymatic degradation
re-uptake

39
Q

describe diffusion in neurotransmitter removal

A

all neurotransmitters are removed from the synaptic cleft to some degree by diffusion

40
Q

describe enzymatic degradation neurotransmitter removal

A

enzyme degradation in the synaptic cleft, e.g. acetylcholine esterase degrades ACh

41
Q

what is the most common mechanism used for inactivation of neurotransmitters

A

re-uptake

42
Q

give an example of hoe reuptake works

A

glutamate transporter removes cultamate to presynaptic terminals and astrocytes, and another form of the transporter moves glutamate to synaptic vesicles for storage

43
Q

each neuron receives thousands of _________; some _____________ and some ____________

A

synapses
excitatory
inhibitory

44
Q

what does each indivdual synapse produce when activated

A

very small postsynaptic potentials at axon initial segment

45
Q

when do the potentials decay

A

when they are passively conducted from dendrites

46
Q

what needs to happen in order to depolarise the initial segment to threshold

A

EPSPs need to be enhanced

47
Q

what is temporal summation

A

when only single excitatory synapse is activated multiple times within short period of time for membrane potential at axon hillock to reach threshold

48
Q

what is spatial summation

A

when more than one excitatory synapse is activated simultaneously (or almost simultaneously) for membrane potential to reach threshold

49
Q

subthreshold means (in terms of summation)

A

no summation occured

50
Q

in order for excitatiry synapses to reach threshold at axon initial segment, ____________ must occur. this is the same for ________

A

summation

EPSPs

CST - BIOSCI107 (13 decks)

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